It's pretty standard. That's why there are so many letter revisions of military equipment, from small arms to aircraft. It's pretty standard in software design,

It's pretty standard. That's why there are so many letter revisions of military equipment, from small arms to aircraft. It's pretty standard in software design, too, for that matter. Just because the 737 MAX has a problem doesn't mean the underlying philosophy that directed the design was a poor one. The philosophy is basically, "keep what works, fix what doesn't." It's basic iterative design.